Relationships Between Avian Species Richness And Environmental Characteristics In North America

Authors(s): D. B. Inkley

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Publication Date: 0000-00-00

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Location: Laramie WY

Abstract: Geographic variation in species richness exhibits certain consistent patterns which deserve explanation. Many hypotheses have been proposed to explain the causes of these patterns. The topographic relief hypothesis suggests that there are many species in rugged terrain. According to the climatic severity hypothesis, benign environments favor high species richness. Highly productive environments support many species if the productivity hypothesis is correct. The seasonality hypothesis proposes that habitats with seasonal environments have few species. And, the predictability hypothesis suggests that low environmental variation between years increases species richness. This study examined relationships between environmental characteristics representing the various species richness patterns of North American birds. Weather stations from throughout North America were selected as sample points. At each sample point environmental characteristics were determined from weather data and topographic maps. Also, for each sample point the number of species present was determined from range maps. Counts of species were made for five separate avian categories. These categories were resident, migrant wintering, total wintering, migrant breeding, and total breeding birds. Simple and multiple regressions were calculated to determine relationships between species richness and environmental characteristics. The topographic relief hypothesis was not supported by the analyses although topographic relief may be important to species richness at a different resolution than that measured in the study. The climatic severity hypothesis was supported. The way in which severe climates directly determine species richness is unclear. The productivity, seasonality, and predictability hypotheses were supported for certain avian groups. Resident, migrant wintering, and total wintering avian species richness were all correlated with winter climatic severity, winter climatic stability, and winter productivity. Species richness of resident birds was strongly correlated with seasonality. Species richness of migrant breeding and total breeding birds could not be explained with the tested hypotheses. Species richness of birds may be limited by winter season environmental conditions.

Keywords: animal, breeding, bird, Aves, ornithology, habitat, Wyoming Cooperative Fish and Wildlife Research Unit, University of Wyoming